What is Becker muscular dystrophy?

Becker muscular dystrophy is a category of muscle-wasting disease caused by a mutation that results in a deficiency or abnormal production of the protein dystrophin (dystrophinopathies). The abnormal gene is called DMD and it is located on the X chromosome. Becker muscular dystrophy follows an X-linked recessive inheritance, so it mainly affects men, but some women are affected. Becker muscular dystrophy usually begins in the teens or early twenties, and symptoms vary greatly between affected people. Muscle atrophy develops slowly but usually requires a wheelchair. In some affected people, the heart muscle becomes weak (cardiomyopathy) and this process can be fatal. There may be learning problems associated with visual skills.

Both the Duchenne and Becker forms of muscular dystrophy are associated with a heart condition called cardiomyopathy. This form of heart disease weakens the cardiac muscle, preventing the heart from pumping blood efficiently. In both Duchenne and Becker muscular dystrophy, cardiomyopathy typically begins in adolescence. Later, the heart muscle becomes enlarged, and the heart problems develop into a condition known as dilated cardiomyopathy. Signs and symptoms of dilated cardiomyopathy can include an irregular heartbeat (arrhythmia), shortness of breath, extreme tiredness (fatigue), and swelling of the legs and feet. These heart problems worsen rapidly and become life-threatening in most cases. Males with Duchenne muscular dystrophy typically live into their twenties, while males with Becker muscular dystrophy can survive into their forties or beyond.

Signs and symptoms of Becker muscular dystrophy

The symptoms of Becker muscular dystrophy usually begin in the teens or late twenties. The first symptoms include numbness during exercise and decreased endurance during exercise. The muscles in the hips, thighs, thighs, and shoulders gradually weaken, causing abdominal cramps. Some muscles (contractions) cannot move due to the contraction of the muscle fibers. The progression of BMD is slower and more variable than Duchenne muscular dystrophy but usually requires a wheelchair. The heart muscle is also affected and there is less shortness of breath, fluid build-up in the lungs, and swelling in the legs and lower legs. Dilated cardiomyopathy is the most common cause of death in people with BMD, and most affected people die in their 40s.

About 5-10% of women who carry the DMD gene have some of the symptoms of muscle weakness that progress slowly or not at all. Muscle weakness (uneven) on one side of the body is usually serious. 

Causes of Becker muscular dystrophy

Becker muscular dystrophy is caused by abnormalities (mutations) in the DMD gene that cause the production of the protein dystrophin. Dystrophin is essential for the stability and protection of muscles. The dystrophin protein is lower than normal and does not function normally due to a genetic mutation.

The DMD gene is located on the X chromosome and follows the X-linked recessive inheritance of Becker muscular dystrophy. Women have two X chromosomes, but one of the X chromosomes is “off” and all the genes on that chromosome become inactive. Women with the disease gene on one of their X chromosomes carry the disorder. Carrier females generally show no symptoms of the disorder because it is generally “aborted” on the X chromosome by an abnormal gene. A man has an X chromosome and if he inherits an X chromosome that contains a gene for the disease, he will develop the disease. Men with X-linked disorders pass the disease gene to all of their daughters, who become carriers. Males do not pass the X-linked gene to their offspring because males always pass their Y chromosome to male offspring instead of their X chromosome. Female carriers of an X-linked disorder have a 25% chance of having it. Own carrier daughter in each pregnancy, a 25% chance of having a non-carrier daughter, a 25% chance that a child will become infected, and a 25% chance of giving birth to an unaffected child. 

How does BMD affect the body?

The weakness of the muscles of the legs, trunk, and pelvis is often the first symptom of BMD. It can cause difficulty in running, jumping, and walking at a normal pace. Patients with more severe symptoms may eventually need a wheelchair.

Although most patients with BMD experience muscle atrophy only in skeletal muscle, this condition also affects the heart muscle, as in DMD. Although BMD does not generally affect life expectancy, it can be fatal if cardiac symptoms do not resolve.

Diagnosis of Becker muscular dystrophy

The diagnosis of Becker muscular dystrophy is complicated because it shares many symptoms with other conditions such as Duchenne, girdle muscular dystrophy, and spinal muscular atrophy.

It is challenging to determine whether the weakness arises in the muscles that control these muscles or in the motor neurons (branches of the spinal cord).

The first step is a careful physical exam and a history of signs and symptoms so that the doctor can observe a pattern of progress. Diagnostic tests for Becker muscular dystrophy:

Blood tests: Genetic blood tests reveal a genetic mutation that causes Becker muscular dystrophy. They can also measure the presence of creatine kinase, an enzyme that is formed when muscle tissue breaks down. This substance increases muscular dystrophy and inflammatory conditions.

Muscle biopsy: For children who do not have clinical evidence of Duchenne muscular dystrophy but have not shown one of the more common mutations, a small sample of muscle tissue is examined under a microscope to confirm the diagnosis.

Electromyogram: This test looks for muscle weakness due to the destruction of muscle tissue without damage to the nerves.

Electrocardiogram (ECG or EKG): A test that records the electrical activity of the heart, an ECG shows abnormal rhythms (arrhythmia or dysrhythmia), and detects damage to the heart muscle.

The heart is mainly muscular and therefore it is affected by muscular dystrophy. Becker muscle dystrophy causes cardiomyopathy, which weakens the heart muscle and, if not observed, can lead to cardiac arrest and transplantation.

Treatment for Becker muscular dystrophy

There is currently no cure for Becker muscular dystrophy. A doctor can prescribe a steroid medicine to help people walk as long as possible.

The clinical course of Becker’s muscular dystrophy is variable. Some may need a wheelchair in their 30s; Others can continue to walk with or without a cane for many years.

Becker is a multidisciplinary team of experts with experience treating muscular dystrophy to help address the symptoms:

Physical and occupational rehabilitation specialists can design exercise programs and teach stretching activities to reduce contractions, which are stiff or deformed joints caused by the contraction of muscles and tendons.

Orthopedic surgeons who specialize in muscular dystrophy can treat contractions and scoliosis.

Cardiologists track a patient’s heart function with EKGs and echocardiograms.

Complications and their handling

The weakness can lead to joint contractions and scoliosis, which may require orthopedic or orthopedic treatment.

Complications of instability, for example, constipation and osteoporosis.

Heart problems

The severity of cardiomyopathy and blood circulation may not parallel the severity of the skeletal muscle disease. Atrial and ventricular arrhythmias can be fatal. The degree of hypoventilation and lung dysfunction also affects cardiac function in muscular dystrophy.

Dilated cardiomyopathy:

It occurs in the majority of patients with BMD. This is an important factor that affects survival.

If the muscle weakness is mild, it can be a manifestation symptom. The severity of cardiac involvement is not related to the severity of skeletal muscle weakness.

Asymptomatic (subclinical) cardiomyopathy is common.

Symptoms can be specific, for example, fatigue, lack of sleep, weight loss, vomiting.

Arrhythmia.

Follow-up and treatment

Regular cardiac monitoring from diagnosis / 10 years of age, including:

• Clinical evaluation.
• Electrocardiogram (ECG) and echocardiogram – These are difficult to understand due to scoliosis.
• Other tests: Cardiac magnetic resonance imaging, multiple acquisition study (MUGA), and tissue Doppler echocardiography may be more helpful than standard echocardiography.
• Treatment consists of standardized rules, for example, angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and diuretics for heart failure.
• Consider the use of anticoagulants as it increases the risk of thromboembolism.
• Nutritional and respiratory function should be optimized.
• Some patients require a heart transplant.
• Intoxication problems
• Malignant rhabdomyolysis (malignant hyperthermia-like reaction) to certain narcotic agents.
• Hyperkalemia in response to succinylcholine.
• The risk of heart disease is high.
• Careful evaluation and monitoring are required with any anesthesia or surgical procedure.

Other issues

Respiratory muscle weakness:

Depending on the clinical severity of the muscle weakness, this is a possible problem. The management of DMD is similar to respiratory problems. See the article on specific Duchenne muscular dystrophy.

Pain in the lower back, spine, and legs.